Power Factor

EXPLANATION In a purely resistive AC circuit, voltage and current waveforms are in step, changing polarity at the same instant in each cycle. Where Reactive loads are present, such as Capacitor s or Inductor s, energy storage in the loads result in a time difference between the current and voltage waveforms. Since this stored energy returns to the source and is not available to do work at the load, a circuit with a low power factor will have higher currents to transfer a given quantity of power than a circuit with a high power factor. Real Power is the capacity of the circuit for performing work in a particular time. Due to reactive elements of the load, the apparent power, which is the product of the voltage and current in the circuit, will be equal to or greater than the real power. The reactive power is a measure of the stored energy that is reflected to the source during each alternating current cycle. (P), measured in Watt s (W); Apparent Power (S), measured in volt-amperes (VA); and Reactive Power (Q), measured in reactive volt-amperes (VAr). The power factor can be expressed as: : $rac{P}{S}$ . In the case of a perfectly sinusoidal waveform, P, Q and S can be expressed as vectors that form a Vector triangle such that: : $S^2\,\! = {P^2\,\!} + {Q^2\,\!}$
	:<math> P	S \left\cos\phi ight </math>

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